JPH0681922B2 - Air amount detection device for internal combustion engine - Google Patents

Description

The present invention relates to an air amount detection device for an internal combustion engine.

(Prior Art) In a fuel injection type internal combustion engine, it is important to accurately detect the amount of air taken into the engine. As a detection device, the amount of air can be directly measured by a flow sensor such as a hot wire type. There are those that are indirectly detected from the internal pressure of the intake pipe measured by the pressure sensor and the engine rotation speed.
In addition to the pressure sensor, a throttle valve opening sensor is provided to detect the air amount from the throttle valve opening and the intake pipe internal pressure (see Japanese Patent Publication No. 61-4981).

(Problems to be Solved by the Invention) However, in the detection device using the flow rate sensor and the pressure sensor as described above, the variation of the detected value due to the intake pulsation is large, and the injection of the fuel injection valve controlled based on this is large. Since the amount fluctuates, the engine torque fluctuates greatly.

Further, since the flow rate sensor and the pressure sensor are not so responsive, there is a problem that the detection error during the transition is large and the cost is high.

On the other hand, in these detection devices, since the air flow rate at the sensor position is detected, the detected value does not match the amount of air flowing into the cylinder during a transition, and in particular, the fuel injection valve is installed in the intake manifold assembly. In the internal combustion engine installed upstream of the section, the amount of air passing through the fuel injection part and the amount of air flowing into the cylinder do not match, so the air-fuel ratio becomes rich or lean during acceleration or deceleration. There is a problem of doing.

An object of the present invention is to solve the above problems and to provide an air amount detection device having good transient response.

(Means for Solving the Problems) The present invention relates to means 1 for detecting the throttle valve opening degree as shown in FIG. 1 in an internal combustion engine in which a fuel injection portion is provided on the upstream side of a collecting portion of an intake manifold. And a means 2 for detecting the engine speed, and a steady air flow rate Q _H from both detected values.
From the steady-state air flow rate calculation means 3 and the delay coefficient calculation means 4 which similarly calculates the delay coefficient K ₂ of the air flow from the detected values, and the steady-state air flow rate Q _H and the delay coefficient K ₂ , the following equation Qcyl =
Delay correction means 5 for calculating the air flow rate Qcyl flowing into the cylinder by Qcylo + K ₂ (Q _H −Qcylo) (where Qcylo is the previously calculated value of Qcyl), coefficient KMANi and delay correction means determined according to the volume of the intake manifold. From the calculated value of ΔCM = KMANi (Qcyl-Qcylo)
An addition amount calculation means 6 for calculating CM and an air flow rate addition means 7 for calculating the passing air flow rate Qainj of the fuel injection unit by adding the cylinder inflow air flow rate Qcyl and the addition amount ΔCM are provided.

(Operation) Thus, from the throttle valve opening and the engine rotational speed, without being affected by the intake pulsation, together with the air flow rate Q _H is detected accurately, throttle valve opening and the engine rotates in the air flow rate Q _H By adding the correction with the delay coefficient K ₂ based on the speed, the air flow rate Qcyl to the cylinder can be accurately detected without deteriorating the responsiveness even during a transient time. Then, by adding a predetermined addition amount ΔCM according to the intake manifold volume to this air flow rate Qcyl, the passing air flow rate Qainj at the fuel injection portion can also be accurately detected.

(Embodiment) FIG. 2 shows a mechanical structure of an embodiment in which the present invention is applied to a single-point injection type engine in which one fuel injection valve 12 is installed in an intake passage 11 upstream of a throttle valve 10. .

14 is a throttle valve opening sensor that detects the opening α of the throttle valve 10, 15
Is a crank angle sensor that detects the engine speed N,
These detection signals are input to the control unit 18 together with signals from a water temperature sensor 16 that detects the engine cooling water temperature, an intake air temperature sensor (not shown) that detects the temperature of intake air, an air-fuel ratio sensor 17 that detects the air-fuel ratio, etc. To be done.

Further, 19 is a passage that bypasses the throttle valve 10, and 20 is an idle control valve that also allows the opening area Ab of the bypass passage 19 to be variable.

The control unit 18 is composed of a microcomputer including a CPU, a RAM, a ROM, an I / O device, etc., and has all the functions of each means 1 to 7 shown in FIG. Fuel injection control of the injection valve 12 is performed. Further, the control unit 18 drives and controls the idle control valve 20 so as to maintain a predetermined engine rotation speed during idling, for example.

Next, the contents executed in the control unit 18 will be described with reference to the flowcharts of FIGS. Note that the control according to the above flow chart shows an example applicable to both the single point injection system and the multipoint injection system in which a fuel injection valve is provided for each intake port.

FIG. 3 shows a calculation routine of the air flow rate Qcyl flowing into the cylinder. First, at step 10, the throttle valve opening sensor
The throttle valve opening area Aα by searching the table from 14 signals α
Is required. FIG. 6 shows a characteristic diagram showing the contents of the table. The opening area Aα changes in proportion to the throttle valve opening α.

In step 11, the opening area Ab of the passage 19 that bypasses the throttle valve 10 is obtained by a table search from the drive control signal (duty signal) ISCD commanding the idle control valve 20.
FIG. 7 shows a characteristic diagram showing the contents of the table. The opening degree of the idle control valve 20 increases as the duty value increases, and the opening area Ab also increases accordingly.

Then, in step 12, the total flow passage area A is calculated from the sum of the throttle valve opening area Aα and the bypass passage opening area Ab.

Next, determine the air flow rate Q _H in the steady against Soryuro area A in step 13, the engine rotational speed N of the case air flow rate Q _H is Soryuro area A from the crank angle sensor 15
It is calculated from the three-dimensional table assigned to the value A / N divided by and the engine speed N. FIG. 8 is a characteristic diagram showing the contents of the table, and the equal air flow rate line has a characteristic of increasing substantially according to A / N. This means that if the rotation speed N is constant, A / N changes according to the throttle valve opening α,
This is because the air flow rate increases as α increases.

In step 14, the delay coefficient K ₂ (K ₂ <K ₂ <K ₂ <K
1) is obtained by a table search from the total flow passage area A and the engine rotation speed N. This search is performed by a three-dimensional table, and FIG. 9 shows a characteristic diagram showing the contents of the table. The delay coefficient K ₂ changes substantially according to the total channel area A.

Then, in step 15, the air flow rate Qcyl to the cylinder is
From the air flow rate Q _H and the delay coefficient K ₂ , Qcyl = Qcyl ₀ + K
It is calculated by the equation of _{2 (Q} H -Qcyl _0). Qcyl ₀ is the air flow rate Qcyl calculated last time, and Qcyl ₀ = Q _H in the steady state.

FIG. 4 shows a calculation routine of the air flow rate Qainj passing through the intake passage 11 of the fuel injection valve 12. First, at step 20, the difference value ΔQcyl (= Qcyl (= the air flow rate Qcyl obtained by the calculation routine of FIG. 3). The addition amount ΔCM can be calculated from Qcyl−Qcyl ₀ ) and the constant KMANi. The pressure value in the intake manifold 21 changes according to the difference value ΔQcyl of the air flow rate Qcyl, that is, the increase / decrease amount of the air flow rate Qcyl, but the air amount that changes the pressure is a constant KMAN determined according to the volume of the intake manifold 21.
The addition amount ΔCM is calculated by multiplying by i.

Then, in step 21, the addition amount ΔCM is added to the air flow rate Qcyl to calculate the air flow rate Qainj. The air flow rate Qainj passing through the fuel injection unit is calculated back based on the increase / decrease amount of the air flow rate Qcyl. It is equivalent to the sum.

In step 22, the air flow rate Qcyl is set to Qcyl ₀ to prepare for the next calculation. In the steady state, of course, ΔCM = 0, Qainj = Q
It becomes cyl.

FIG. 5 shows a calculation routine of the fuel injection amount Ti of the fuel injection valve 12. In the case of the single point injection method as shown in FIG. 2, the process goes to steps 30 to 31, and the basic fuel injection amount Tp is Atmospheric pressure correction coefficient Kp for flow rate Qainj
It is calculated by multiplying a, the intake air temperature correction coefficient KTa, and the constant Ka.

Further, for example, when applying to a multi-point injection method in which a fuel injection valve is installed in each intake port, go to steps 30 to 32, the basic injection amount Tp is the air flow rate Qcyl atmospheric pressure correction coefficient Kpa, intake air temperature correction It is obtained by multiplying the coefficient KTa and the constant Ka.

Then, in step 33, each basic injection amount Tp is multiplied by various correction coefficients COEF conventionally used and the feedback correction coefficient LAMBDA from the air-fuel ratio sensor 17, and the invalid pulse width (voltage correction amount) Ts is further added to perform fuel injection. The amount Ti is required.

Each routine is executed at predetermined time intervals or in synchronization with engine rotation.

In this way, the air flow rate Q _H is calculated based on the opening α of the throttle valve 10 (and the opening of the bypass passage 19 of the throttle valve 10) and the engine rotation speed N. It is not affected by intake pulsation unlike when using a sensor, and it is possible to maintain good responsiveness during transient changes in engine operating conditions, and to obtain an accurate detected value of air flow rate Q _H. can get.

On the other hand, the air flow rate Q _H does not match the air flow rate Qcyl flowing into the cylinder due to the air flow delay except in the steady state, but the air flow delay corresponds to the throttle valve opening α and the engine rotation speed N. , The delay coefficient based on α and N
The K _2, by adding a correction to the air flow rate Q _H, airflow Qcyl to the cylinder during the transient is determined accurately.

Therefore, in the case of the multi-point injection method, by calculating the fuel injection amount based on the air flow rate Qcyl, accurate fuel injection control becomes possible, which results in excessive fuel injection amount Ti during acceleration and deceleration. As described above, the proper air-fuel ratio can be maintained as in the steady state.

Fig. 10 shows the operating characteristics during acceleration. The air flow rate Q _H corresponds to the rapid opening of the throttle valve 10, whereas the air flow rate to the cylinder gradually increases close to Qcyl. When fuel is injected into the intake port according to the air flow rate Q _H , the air-fuel ratio is greatly enriched (similar to the conventional example), but by injecting fuel according to the air flow rate Qcyl, a substantially constant air-fuel ratio is obtained. You can get it.

On the other hand, in the case of the single point injection method, the air flow rate Qain passing through the fuel injection valve 12
The fuel injection amount is calculated based on j to control the fuel injection. This air flow rate Qainj is obtained by adding the addition amount ΔCM corresponding to the increase / decrease in the pressure in the intake manifold 21 to the air flow rate Qcyl. Desired.

Here, the steady-state flow rate of the air flow rate Qainj, Q _H , Qcyl is
Qainjo, _{Q H} o, as _{Qcylo (Qainjo = Q H o =} Qcylo),
When Q _{H o} by opening operation of the throttle valve 10 becomes Q _H, Qcyl flowing into the cylinder, as shown in FIG. 12 equilibrated in Q _H and gradually increases from Qcylo, Qainj fuel injection unit, Qainj
After increasing momentarily from o, it gradually decreases and equilibrates with Q _H , but at this time, Qcyl increases according to the difference with Qainj. Therefore, the addition amount ΔCM calculated from the increase amount Qqyl ΔQcyl By adding to Qcyl, Qainj will be obtained. It has been confirmed by experiments that the air flow rate Qainj detected in this way substantially matches the true value flow rate.

Therefore, even in the case of the single point injection method, it is possible to perform accurate fuel injection control, and it is possible to always maintain an appropriate air-fuel ratio according to the air flow rate Qainj during steady state, acceleration, deceleration, etc.

FIG. 11 shows the operation characteristics at the time of acceleration.For the rapid opening of the throttle valve 10, the air flow rate Qainj passing through the fuel injection portion upstream of the throttle valve 10 temporarily increases, but then decreases, At this time, for example, when the amount of fuel injected according to the opening α of the throttle valve 10 is injected, the air-fuel ratio becomes largely lean (conventional example), but by injecting the fuel according to the air flow rate Qainj, a substantially constant air-fuel ratio is obtained. The air-fuel mixture can be sucked into the cylinder.

It should be noted that in FIGS. 10 and 11, the air-fuel ratio is somewhat leaner, which is an error due to an increase in the adhered fuel in the intake pipe during acceleration.

(Effect of the Invention) As described above, according to the present invention, by correcting the steady-state air flow rate calculated from the throttle valve opening degree and the engine rotation speed with the delay coefficient according to the operating state, the cylinder in the transient state can be obtained. The flow rate of air to the cylinder can be accurately detected, and the flow rate of air passing through the fuel injection part can be accurately detected by adding a predetermined amount to the flow rate of air to the cylinder. Therefore, even in an internal combustion engine of single-point injection type. The transient air-fuel ratio control can be accurately performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the present invention, FIG. 2 is a mechanical block diagram showing an embodiment of the present invention, FIGS. 3 to 5 are flow charts showing the contents of respective calculations, and FIG. FIGS. 9 to 11 are characteristic diagrams showing the contents of each table used for calculation, FIGS. 10 and 11 are explanatory diagrams showing the operating characteristics at the time of acceleration, and FIG. 12 shows the relationship between the air flow rates at the time of acceleration. FIG. 1 ... Throttle valve opening detection means, 2 ... Engine rotation speed detection means, 3 ... Steady air flow rate detection means, 4 ... Delay coefficient calculation means, 5 ... Delay correction means, 6 ... Addition amount calculation means , 7
...... Air flow rate addition means.

Front Page Continuation (72) Inventor Hiromichi Miwa 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Inventor Toshio Takahata Takaracho, Kanagawa-ku, Yokohama City, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Invention Person Yasuo Kiyomiya 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. In an internal combustion engine having a fuel injection portion provided upstream of a collection portion of an intake manifold, a means for detecting a throttle valve opening, a means for detecting an engine rotation speed, and a steady detection from both detection values. delay coefficient K ₂ of the constant air flow rate calculation means for calculating an air flow rate Q _H, also from both the detected value of the air flow
A delay coefficient calculating means for calculating a steady air flow rate Q _H and the delay coefficient K ₂ Metropolitan from: _{Qcyl = Qcylo + K 2 (Q} H -Qcylo)
(However, Qcylo is the previous calculated value of Qcyl) The delay correction means that calculates the air flow rate Qcyl flowing into the cylinder, the coefficient KMANi determined according to the volume of the intake manifold, and the calculated value of the delay correction means, the following formula ΔCM = KMANi (Qcyl−Qcy
lo)) and an addition amount calculating means for calculating a predetermined addition amount ΔCM, and an air flow rate adding means for calculating the passing air flow rate Qainj of the fuel injection unit by adding the cylinder inflow air flow rate Qcyl and the addition amount ΔCM. An air amount detecting device for an internal combustion engine, comprising: